Method of curing flaps for pneumatic tire casings



April 5, 1932. c. E. MAYNARD 1,852,085

METHOD OF CURING FLAPS FOR PNEUMATIC TIRE CASING? Filed Dec. 5, 1929 I N V EN TOR.

Char/es [dyer Ma /10rd.

' ATTORNEY.

Fatentecl Apr. 5, 1932 CHARLES EDGAR MAYNARD, 0F nonrmmrir on, FISK RUBBER COMPANY, or outcome iaAss cHUsET'rs, A CORPORATION OF MASSACHUSETTS METHOD OF comm; FLAPS rorti ikinmlfn'rio Tins olisfiids Application filed December 5, 1929. Serial No. 411,80'.

My invention relates to a method of vulcanizing or curing rubber flaps, such as are used in pneumatic tire casings.

It is customary in the manufacture of rubber flaps to eXtrude the rubber material in lengths or lengths having a cross-sectional shape approximating that desired in the finished article. If individual annular or endless flaps are desired, suitable lengths are cut,

the ends spliced and the annulus placed on a by tensioning the stock as it is placed on the former.

It is found that certain rubber compounds, which it is in some cases desirable to use in the manufacture or" these flaps, lack sufiicient elasticity in the uncured state with the result that when such stocks are stretched onto the ring or drum formers they take a permanent elongation so that the desired snug fit on the curing former is not secured. During the initial part of the cure such stocks also tend to sag under their own Weight, further loosening the material on the form.

it is the object of my invention to overcome the above-mentioned difficulties and provide a method of curing stocks which lack elasticity in their uncured state on the conventional rings and drums.

I ve found that suiiicient elasticity may be imparted to these normally inelastic uncured stocks by a partial vulcanization or cure and broadly stated my method comprises partially curing the stock under conditions such that substantially no dlstorting tension or mechanical pressure is applied to the stock and complete support is afforded the stock whereby sagging or permanent elongation is avoided.

My invention will now be more specifically described with reference to the accompanying drawings which illustrate one embodi=.

ment ofzmyinventionr W r Fig. 1" isv an isom'etric figure showing the first stepj o'fmy method appliedto the curing of endless or annulxrfiapsp.

.Fig. 2' is a view, partially broken away, showing thering or. former used in" curing endless flaps;

Fig. 3 is 8; Fig.2; Fig. l; showing tlie first step .in curing long lengths of flap material; and Figu'tiis a view of he former or drum used in curing long lengths of flap 1naterial;

l nthe drawings, Figs. land' illustrate view taken on line of the first step in my method, the flap material being shown in endless form at 10 in Fig. 1 and in long lengths at 11- in Fig-:4. In the endless form (Figl 1) the extruded stock is cut to length,'spliced and placed on trays 12, the looped ends13 of the flaps beingsupported by'bars 14, thesebars' preventingsharp folds being'v formed of the looped ends during curing. Bars Mare spaced from the bot-- tomgot'the trays sulficiently to permit the stock to be freely positioned between the bar and the tray.

The long lengths of flap matrial 11 are treatedthe-'same'as' the endless flaps l O;*b'eingloopedover a tray 15 (Fig. 4:)", the looped ends 16 beingsupported bybars 17'. These bars do not rest on the material 11 butare raised as by blocks-18 so thatrio weightis placed on the stock..

The material on the tiraysis" placed in a heateror vulcanizerand given a short'pre liminary cure, such as" a tl'iree minute rise to a sixty pound steain'pressure. .Thistime limit and pressure may' be varied fonvarying stocks ,'but the cure mustbe of such'length asto prevent blistering of the material but not long enough to give the'rnater ia'l" a permanent set which cannot be removed or cha nge'd 1 during subsequentheating. The flap material'is then?cooled'in the vulcaniz e r. by coldwater or allowed to cool in the air. This shortpreliminary; cure imparts tothe material suflicient coherence and elasticity that,

with subsequent-heating it will: no longer is a view corresponding to Fig; 1

take a permanent elongation under reason able tension or stretch under its own Weight as heretofore. v

The material is now placed on the formers, the endless flap 10 on an annular ring former 19 and the long lengths 11 on a spiral shaped former 20 under sufficient tension to cause the stock to hug the former, and again returned to the heaters Where it is given a long enough second heat to complete the cure. 7

By my method a large variation in compoundingis made possible to meet various requirements in the properties or character of the finished product.

Having thus described my invention, I claim:

1. The method of curing rubber flap ma terial Which comprises giving vthe partially formed uncured material a short open heat cure While the material is completely supported and untensioned, and giving the material a finish cure While positioned on formers under tension.

. 2. The method of curing rubber flap material Which comprises giving the partially formed uncured material a partial open heat cure, While thematerial is completely supported and untensioned, of sufficient length to. impart elasticity to the material and to prevent blistering but short of a permanent setting cure, and finally giving the material a finish cure While positioned on formers under tension.

3. The method of curing rubber flap material which comprises giving the material a partial open heat cure, While the material is completely supported and untensioned, of sufiicient length to impart elasticity to the material and to prevent blistering but short of a permanent setting cure, and finally giving the material a finish cure While positioned on formers under tension.

at. The method of curing rubber flap material Which comprises giving the material a partial open heat cure, the degree of which is such to obviate flow of the rubber under subsequent curing and leaving the material flexible and elastic, and giving the material a subsequent finishing cure When positioned on formers. v

5. The method of curing rubber flap material which comprises looping the material on trays, supporting the looped ends thereby preventing sharp folds being formed at these ends, giving the material When so positioned a partial cure, cooling the partially cured material, placing the cooled material on formers under tension, and giving the material a finish cure.

6. The method of curing rubberflap material which comprises looping the material on trays, supporting the looped ends thereby preventingsharp folds-from being formed at these ends, giving the material a partial cure the degree of Which is such to obviate flow of and giving the material a subsequent finish cure.

CHARLES EDGAR MAYNARD. 

